Abstract
Molybdenum carbides with various C/Mo atomic ratios were synthesized on γ-Al2O3 using a vertical tube hot-wall chemical vapor deposition (CVD) reactor in a stream of MoCl5, benzene, and hydrogen at 1000 K and total pressure of 0.13 kPa. The activities of the molybdenum carbide catalysts (CVD catalyst) prepared by CVD method were tested for the hydrogenation of CO2 at 573 K and atmospheric pressure in comparison with those by the temperature-programmed reaction (TPR catalyst). The ratio of the C 1s peak of carbidic carbon to the Mo 3d peak of the alumina-supported molybdenum carbide, prepared by changing the benzene/MoCl5 ratio was determined by XPS spectroscopy. The relationship between the turnover frequency and the C/Mo ratio of molybdenum carbides for CO2 hydrogenation was discussed. The turnover freqencies of the CVD catalysts were 0.35-0.5 s-1 and higher than those of the TPR catalysts.
